Compatible organic osmolytes in rat liver sinusoidal endothelial cells.
Compatible organic osmolytes, such as betaine and taurine are involved in the regulation of Kupffer cell (KC) function, but nothing is known about osmolytes in liver endothelial cells. This was investigated here by studying the effect of aniso-osmotic exposure of rat liver sinusoidal endothelial cells (SEC) on osmolyte transport and the messenger RNA (mRNA) levels for the transport systems for betaine (BGT1), taurine (TAUT), and myo-inositol (SMIT). Compared with normo-osmotic exposure (305 mosmol/L), hyperosmotic exposure (405 mosmol/L) of SEC led to an increase in the mRNA levels for these transport systems and simultaneously to a stimulation of betaine, taurine, and myo-inositol uptake, which led to an increase of cell volume. Conversely, hypo-osmotic exposure decreased osmolyte uptake. When hyperosmotically pre-exposed SEC were loaded with betaine, taurine, or myoinositol, hypo-osmotic stress stimulated the efflux of these osmolytes from the cells. Studies on osmolyte tissue levels revealed that taurine was an important compatible organic osmolyte under normo-osmotic conditions and predominantly released following hypo-osmotic stress. Conversely, following hyperosmotic exposure, the increase in cellular betaine and myo-inositol exceeded that of taurine. In lipopolysaccharide (LPS)-treated SEC, hyperosmotic exposure markedly raised the mRNA levels for cyclo-oxygenase-2 (COX-2), but not for inducible nitric oxide synthase (iNOS). The increase of COX-2 mRNA levels was counteracted by betaine and taurine and, to a lesser extent, by myo-inositol. The findings indicate that SEC use taurine, betaine, and myo-inositol as compatible organic osmolytes.
Weik
C
C
Medizinische Universitätsklinik, Heinrich Heine University, Düsseldorf, Germany.
Warskulat
U
U
Bode
J
J
Peters-Regehr
T
T
Häussinger
D
D
D000818:Animals; D001622:Betaine / Q000378:metabolism*; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D004727:Endothelium / Q000187:drug effects / Q000378:metabolism; D050485:GABA Plasma Membrane Transport Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism; D007294:Inositol / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009994:Osmolar Concentration; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D027981:Symporters; D013654:Taurine / Q000378:metabolism*; D013997:Time Factors; D000099247:Taurine Transporters
D001622:Betaine; D002352:Carrier Proteins; D051546:Cyclooxygenase 2; D050485:GABA Plasma Membrane Transport Proteins; D006360:Heat-Shock Proteins; D007294:Inositol; D007527:Isoenzymes; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D011451:Prostaglandin-Endoperoxide Synthases; D012333:RNA, Messenger; D027981:Symporters; D013654:Taurine; D000099247:Taurine Transporters; C072207:betaine plasma membrane transport proteins; C073884:SLC5A3 protein, human; C496318:Nos2 protein, rat